Bottlenose dolphins have been washing up dead in record numbers on the shores of the Gulf of Mexico, and so far scientists aren't sure why.

Between February 2010 and this month, over 400 dolphins were either found stranded on the beach or were reported dead offshore. Most of the dolphins have been very young, often either preterm or neonatal, and many were less than 115 centimeters.

The National Oceanic and Atmospheric Administration has designated these deaths as an "unusual mortality event" or UME. A UME is defined by NOAA as an unexpected stranding incident or a significant loss of any marine mammal population.

NOAA is reportedly working with a number of different agencies to try to determine why the bottlenose dolphins are turning up in such large amounts and why they are so young.

Dolphins, like many marine mammals are highly susceptible to dangers like algal blooms, infectious diseases, temperature and environmental changes, and human impact.

Some experts have conjectured that the dolphin deaths could be related to the massive BP oil spill that flooded the gulf in 2010. Since the spill started last April, 15 bottlenose dolphins have been found with confirmed or suspected oil on their carcasses. Mase says that one was found as recently as two weeks ago.

Nine oiled dolphins have been found since last November. Of those nine, six were confirmed to contain oil from the BP spill; one was discovered with oil that did not match the BP spill samples, and two haven't been tested yet.

But Mase says it's possible that the spill isn't the true culprit for the mass of deaths.

"Even though they have oil on them, it may not be the cause of death," she said. "We want to look at the gamut of all the possibilities."Source: CNN